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  1. #1

    Default WONT PASS SMOG!! running too rich!

    went to take my biannual smog test to renew the registration today and failed, ran too rich and cant figure out why?


    ran it to get more than warm enough before showing up for the test, havnt made any changes to the fuel system. still dont know whats wrong. if anyone has tips or checks id gretaly appreciate it before spending the over priced fee of getting the diagnostic.



    the test results:
    Hydrocarbons max @ 15 mph is 118 ppm/ MINE was 172 FAIL
    Hydrocarbons max @ 25 mph is 98 ppm/ MINE was 156 FAIL

    CO max @ 15 mph is 0.68%/ MINE was 1.07% FAIL
    CO max @ 25 mph is 0.87% / MINE was 0.56% PASS

    thanks!!
    90' Chevy Silverado 1500
    Suspension: Belltech 2" Drop Spindles
    Paint/Body: Silver Metalic w/ Red & White pinstriping, steel cowl induction hood, custom billet grille
    Interior/Electronics: Under Construction
    Wheels/Tires: American Racing Chrome Baja 17x8 / Wrapped in TOYO Proxes ST II
    Engine/Trans/Perf: EFI 5.7 Liter 350 cid V-8 w/ 700R4 Trans.
    K&N 57 Series FIPK II CAI
    40 series Flows

    HOORAH SEABEE's!! :fighting0037:SHOOT TO KILL!!


  2. #2

    Default

    My 89 Suburban didn't pass a couple of years ago and it seemed to run fine. We replaced the EGR, no change. Did a full tune-up, no change. Replaced the Cat, passed with flying colors.
    Gary

    99 K 1500 Suburban
    78 Silverado Big 10 w/factory 454
    00 S-10 Blazer
    1976 Trans Am
    1980 Honda CB900 Custom

  3. #3

    Default

    yea i was thinking it might be the cat, although i did put the cat thats on it in new about 6 years ago, i wouldnt think it would go bad that fast.

    i did recentlly change out my spark plugs before taking the test because it was lagging in take off power and found one of them (or maybe more) had been burnt up and wasnt combusting (dead cylinder).

    do you think because of those cylinders not firing over time could have jacked up the cat converter because of all that air and fuel mixture going through unburnt?

    i just dont want to waste the money on a diagnost. if i can figure it out myself. lol
    90' Chevy Silverado 1500
    Suspension: Belltech 2" Drop Spindles
    Paint/Body: Silver Metalic w/ Red & White pinstriping, steel cowl induction hood, custom billet grille
    Interior/Electronics: Under Construction
    Wheels/Tires: American Racing Chrome Baja 17x8 / Wrapped in TOYO Proxes ST II
    Engine/Trans/Perf: EFI 5.7 Liter 350 cid V-8 w/ 700R4 Trans.
    K&N 57 Series FIPK II CAI
    40 series Flows

    HOORAH SEABEE's!! :fighting0037:SHOOT TO KILL!!


  4. #4
    Jr. Mechanic Blazerado's Avatar
    Join Date
    Apr 2009
    Location
    The Dena, Maryland
    Posts
    139

    Default

    Use a scanner and check your O2 sensors. If they dont come out of closed loop it can cause the same issue.

  5. #5

    Default

    Your cat is probably shot. Running raw fuel through it will kill it prematurely. A bad O2 sensor will set an O2 code.
    Jim

    2004 SILVERADO 2500HD LS
    Pro Comp Leveling Kit
    285-75-16 Cooper ST All Terrains
    Pro Comp Programmer
    Bilstein Shocks
    Linux Bed Liner
    Tinted Windows



    Other rides:

    1967 Landcruiser <350 Chevy>
    1970 Camaro
    1990 Geo Metro Convertible
    2007 FJ Cruiser

  6. #6

    Default

    thats what i figured.

    takeing it in for diag. scan on mon, let yall know the results.

    thanks for the help as always!!
    90' Chevy Silverado 1500
    Suspension: Belltech 2" Drop Spindles
    Paint/Body: Silver Metalic w/ Red & White pinstriping, steel cowl induction hood, custom billet grille
    Interior/Electronics: Under Construction
    Wheels/Tires: American Racing Chrome Baja 17x8 / Wrapped in TOYO Proxes ST II
    Engine/Trans/Perf: EFI 5.7 Liter 350 cid V-8 w/ 700R4 Trans.
    K&N 57 Series FIPK II CAI
    40 series Flows

    HOORAH SEABEE's!! :fighting0037:SHOOT TO KILL!!


  7. #7

    Default

    Diagnose it properly. Running rich will kill cats, but replacing the cat doesn't fix the running rich problem, which means the new cat will have a short life.

    I'm not familiar with diagnostics on the TBI motors. Back when I had an '88, you could pull trouble codes by simply jumpering two terminals on the ALDL -- I fully expect your '90 has the same functionality: http://www.troublecodes.net/GM/ If the SES/CEL has come on, I'd probably start by pulling codes (as easy as it is, I might pull codes even if it hasn't been on). The primary function of the engine management (aka OBD1 system) is to control fuel mixture.

    I don't know how to check fuel pressure on the TBI motors, but high fuel pressure can cause a rich condition. Check for leaks into the throttle body/intake (such as a leaky injector) which can cause a rich condition.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  8. #8
    Jr. Mechanic bd1326's Avatar
    Join Date
    Feb 2009
    Location
    Chardon, Ohio
    Posts
    84

    Default

    you ever thought of moving out of cali? no more failed smog test
    bd1326

    2005 Chevy Silverado 6.0 Vortec 4X4
    K&N Air Filter: Stock Replacement
    E3 Spark Plugs
    Magnaflow Single Exit Exhaust
    Rough Country Leveling Kit
    Skyjacker Add-a-Leaf
    Much More To Come


    "Understeer is hitting the wall with the front of your car. Oversteer is hitting it with the rear."
    - NASCAR driver "Fireball" Roberts.

  9. #9
    Sr. Engineer tigersdl65's Avatar
    Join Date
    May 2009
    Location
    Tallassee, Alabama
    Posts
    384

    Default

    Quote Originally Posted by bd1326 View Post
    you ever thought of moving out of cali? no more failed smog test
    Im in bama and of course we dont do that but mine was so bad it smelled funny.
    Schrub!:sign0011:

  10. #10

    Default

    Quote Originally Posted by MrShorty View Post
    Diagnose it properly. Running rich will kill cats, but replacing the cat doesn't fix the running rich problem, which means the new cat will have a short life.

    I'm not familiar with diagnostics on the TBI motors. Back when I had an '88, you could pull trouble codes by simply jumpering two terminals on the ALDL -- I fully expect your '90 has the same functionality: http://www.troublecodes.net/GM/ If the SES/CEL has come on, I'd probably start by pulling codes (as easy as it is, I might pull codes even if it hasn't been on). The primary function of the engine management (aka OBD1 system) is to control fuel mixture.

    I don't know how to check fuel pressure on the TBI motors, but high fuel pressure can cause a rich condition. Check for leaks into the throttle body/intake (such as a leaky injector) which can cause a rich condition.

    i was told before to try this to see what codes come up but i figure i might as well go through with the full diagnostic, luckily a buddy has a shop and is taking care of it for me otherwise id be out about $100 to run it. if it wasnt for that id be doing the paper clip method for sure, lol.

    and i wish i could move out of cali for all the troubles here and stupid laws, unfortunately the pleasures outweigh the pains.

    90' Chevy Silverado 1500
    Suspension: Belltech 2" Drop Spindles
    Paint/Body: Silver Metalic w/ Red & White pinstriping, steel cowl induction hood, custom billet grille
    Interior/Electronics: Under Construction
    Wheels/Tires: American Racing Chrome Baja 17x8 / Wrapped in TOYO Proxes ST II
    Engine/Trans/Perf: EFI 5.7 Liter 350 cid V-8 w/ 700R4 Trans.
    K&N 57 Series FIPK II CAI
    40 series Flows

    HOORAH SEABEE's!! :fighting0037:SHOOT TO KILL!!


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